High performance, low cost receiver front end

Abstract

A radio frequency (RF) receiver front end includes an RF attenuator for receiving an RF input signal and a low noise amplifier (LNA). In one form, the LNA provides a differential output signal and includes a first polarity amplifier and a plurality of second polarity amplifiers. The first polarity amplifier has an input terminal coupled to the output of the RF attenuator, an output terminal for providing a first component of the differential RF output signal, and has a first input impedance. Each of the plurality of second polarity amplifiers has an input terminal coupled to the output of said RF attenuator, and an output terminal. The output terminals of said plurality of second polarity amplifiers are coupled together and form a second component of the differential RF output signal. Each of the plurality of second polarity amplifiers has a second input impedance higher than the first input impedance.

What is claimed is: 
     
       1. A radio frequency (RF) receiver front end, comprising:
 an RF attenuator having an input for receiving an RF input signal, and an output; and 
 a low noise amplifier (LNA) having an input coupled to said output of said RF attenuator, and an output for providing a differential RF output signal, 
 wherein said LNA comprises:
 a first polarity amplifier having an input terminal coupled to said output of said RF attenuator, and an output terminal for providing a first component of said differential RF output signal, said first polarity amplifier having a first input impedance; and 
 a plurality of second polarity amplifiers, each having an input terminal coupled to said output of said RF attenuator, and an output terminal, wherein said output terminals of said plurality of second polarity amplifiers are coupled together and form a second component of said differential RF output signal, and each of said plurality of second polarity amplifiers has a second input impedance higher than said first input impedance. 
 
 
     
     
       2. The RF receiver front end of  claim 1 , wherein said first input impedance substantially matches an impedance of a signal source providing said RF input signal. 
     
     
       3. The RF receiver front end of  claim 1 , wherein said first polarity amplifier comprises a non-inverting amplifier. 
     
     
       4. The RF receiver front end of  claim 3 , wherein said non-inverting amplifier comprises:
 a resistor having first terminal coupled to a power supply voltage terminal, and a second terminal for providing positive component of said differential RF output signal; and 
 a transistor having a first current electrode coupled to said second terminal of said resistor, a gate for receiving a gate bias voltage, and a second current electrode coupled to said output of said RF attenuator. 
 
     
     
       5. The RF receiver front end of  claim 1 , wherein said plurality of second polarity amplifiers comprises two inverting amplifiers. 
     
     
       6. The RF receiver front end of  claim 5 , wherein said plurality of second polarity amplifiers comprises:
 a first transistor having first current electrode coupled to a first power supply voltage terminal, an input electrode coupled to said output of said attenuator, and a second current electrode; and 
 a second transistor having first current electrode coupled to said second current electrode of said first transistor, an input electrode coupled to said output of said RF attenuator, and a second current electrode coupled to a second power supply voltage terminal; and 
 a resistor having a first terminal for receiving a bias voltage, and a second terminal forming said second component of said differential RF output signal and coupled to said second current electrode of said first transistor and to said first current electrode of said second transistor. 
 
     
     
       7. The RF receiver front end of  claim 6 , further comprising first and second capacitors coupled between said output of said attenuator and said input electrodes of said first and second transistors, respectively. 
     
     
       8. The RF receiver front end of  claim 1 , wherein said plurality of second polarity amplifiers comprises four amplifiers. 
     
     
       9. The RF receiver front end of  claim 8 , wherein said plurality of second polarity amplifiers comprises:
 a first transistor having first current electrode coupled to a first power supply voltage terminal, an input electrode coupled to said output of said RF attenuator, and a second current electrode; and 
 a second transistor having first current electrode coupled to said first power supply voltage terminal, an input electrode coupled to said output of said RF attenuator, and a second current electrode coupled to said second current electrode of said first transistor; and 
 a third transistor having first current electrode coupled to said second current electrodes of said first and second transistors, an input electrode coupled to said output of said RF attenuator, and a second current electrode coupled to a second power supply voltage terminal; 
 a fourth transistor having first current electrode coupled to said second current electrodes of said first and second transistors, an input electrode coupled to said output of said RF attenuator, and a second current electrode coupled to said second power supply voltage terminal; and 
 a resistor having a first terminal for receiving a bias voltage, and a second terminal forming said second component of said differential RF output signal and coupled to said second current electrodes of said first and second transistors and to said first current electrodes of said third and fourth transistors. 
 
     
     
       10. The RF receiver front end of  claim 9 , further comprising first, second, third, and fourth capacitors coupled between said output of said RF attenuator and said input electrodes of said first, second, third, and fourth transistors, respectively. 
     
     
       11. The RF receiver front end of  claim 1 , wherein said RF attenuator comprises:
 a first variable attenuator having an input terminal for receiving said RF input signal, an output terminal, and a control input terminal for receiving a first control signal; 
 a second variable attenuator having an input terminal coupled to said output terminal of said first variable attenuator, an output terminal coupled to said input of said LNA, and a control input terminal for receiving a second control signal; and 
 a shunt attenuator having first terminal coupled to said output terminal of said second variable attenuator, a second terminal coupled to a power supply voltage terminal, and a control input terminal for receiving a third control signal. 
 
     
     
       12. The RF receiver front end of  claim 11 , wherein said first variable attenuator comprises:
 a first variable resistor having a first terminal forming said input terminal of said first variable attenuator, a second terminal forming said output terminal of said first variable attenuator, and a control input terminal for receiving said first control signal; and 
 a second variable resistor having a first terminal coupled to said first terminal of said first variable resistor, a second terminal coupled to said power supply voltage terminal, and a control input terminal for receiving said first control signal. 
 
     
     
       13. The RF receiver front end of  claim 11 , wherein said second variable attenuator comprises:
 a first variable resistor having a first terminal forming said input terminal of said second variable attenuator, a second terminal forming said output terminal of said second variable attenuator, and a control input terminal for receiving said second control signal; and 
 a second variable resistor having a first terminal coupled to said first terminal of said first variable resistor, a second terminal coupled to said power supply voltage terminal, and a control input terminal for receiving said second control signal. 
 
     
     
       14. The RF receiver front end of  claim 11 , wherein said shunt attenuator comprises:
 a variable resistor having a first terminal coupled to said output terminal of said second variable attenuator, a second terminal coupled to said power supply voltage terminal, and a control input terminal for receiving said third control signal. 
 
     
     
       15. The RF receiver front end of  claim 11 , further comprising:
 a controller for providing said first, second, and third control signals. 
 
     
     
       16. A radio frequency (RF) receiver, comprising:
 a bonding pad for receiving an RF input signal; 
 an RF attenuator having an input coupled to said bonding pad, and an output; and a low noise amplifier having an input coupled to said output of said RF attenuator, 
 and an output for providing a differential RF output signal, wherein said LNA comprises: 
 a first polarity amplifier having an input terminal coupled to said output of said RF attenuator, and an output for providing a first component of said differential RF output signal; and 
 a second polarity amplifier having an input terminal coupled to said output of said RF attenuator, and an output terminal for providing a second component of said differential RF output signal, and 
 an inductor having a first terminal coupled to said bonding pad, and a second terminal coupled to a power supply voltage terminal, wherein said inductor is coupled between said bonding pad and said power supply voltage terminal so as to provide a direct current (DC) path from said first polarity amplifier through said RF attenuator and through said bonding pad to said power supply voltage terminal. 
 
     
     
       17. The RF receiver of  claim 16 , wherein said inductor is integrated with said bonding pad, said RF attenuator, and said LNA on a single integrated circuit chip. 
     
     
       18. The RF receiver of  claim 16 , wherein said bonding pad, said RF attenuator, and said LNA are combined on a single integrated circuit chip, and said inductor is external to said single integrated circuit chip. 
     
     
       19. The RF receiver of  claim 16 , wherein said first polarity amplifier has a direct current (DC) path through said RF attenuator, said bonding pad, and said inductor, and said second polarity amplifier comprises a plurality of second polarity amplifiers having output terminals coupled together to form said second component of said differential RF output signal.